GASTROENTEROPANCREATIC NEUROENDOCRINE TUMORS CONTAIN A COMMON SET OF SYNAPTIC VESICLE PROTEINS AND AMINO-ACID NEUROTRANSMITTERS

Human neuroendocrine tumours of the gastroenteropancreatic system cont ain major integral membrane proteins of small synaptic vesicles of neu rons, together with characteristic membrane polypeptides of large dens e-core vesicles of neurons and neuroendocrine cells. The membrane poly peptides characteristic for small synaptic and large dense-core vesicl es are detected in pheochromocytomas (n=6), functional (n=6) and non-f unctional (n=6) foregut, and midgut carcinoids (n=17). All gastroenter opancreatic tumours contain large amounts of amino acid neurotransmitt ers, i.e. glycine and glutamate. Upsilon-Aminobutyric acid, however, i s only found in some foregut carcinoids. Thus, neuroendocrine gastroen teropancreatic tumours possess a vesicle type with a content and membr ane composition similar to small synaptic vesicles of neurons.